Fig. 2.

Characterization of InsP₃-evoked⁴⁵Ca²⁺ release from resealed SPM vesicles. A, InsP₃- or A-23187-evoked ⁴⁵Ca²⁺release. Data in the figure are representative results. Resealed SPM vesicles preloaded with⁴⁵Ca²⁺ were perfused at a flow of 1 ml/min in TMC buffer. Each 1 min perfusate was collected for measurement of radioactivity. Results represent⁴⁵Ca²⁺ (cpm) released/mg protein of SPM. Vehicle, InsP₃ (5 μm), or A-23187 (5 μm) was added to the perfusion medium at the indicated time. B, Blockade of InsP₃-evoked⁴⁵Ca²⁺ release by pretreatment with A-23187. C, Lack of effect on InsP₃-evoked⁴⁵Ca²⁺ release by pretreatment with EGTA. D, No significant InsP₃-evoked⁴⁵Ca²⁺ release in the case with 10 nm[⁴⁵Ca²⁺]_i(n = 3). Results represent the fractional release (%) as described in Results. E, InsP₃-evoked⁴⁵Ca²⁺ release (fractional release/%) in the case with 100 nm[⁴⁵Ca²⁺]i (n = 3). F, [⁴⁵Ca²⁺]i dependency of InsP₃-evoked⁴⁵Ca²⁺ release (n = 3). InsP₃-evoked⁴⁵Ca²⁺ release was described in Results. G, Concentration-dependent inhibition of InsP₃-evoked⁴⁵Ca²⁺ release by saponin.H, Concentration-dependent inhibition of InsP₃-evoked⁴⁵Ca²⁺ release by heparin.